Industrial Applicability
The invention relates to an air pressure control valve of an air clutch for controlling the air pressure supplied to the air clutch.
Prior Art and the Problem
A prior art air clutch is constructed as illustrated in FIG. 4.
In FIG. 4, illustrating an air clutch for an automobile, flywheel 10, associated with an engine, to which a clutch cover 12 is fixed to form an annular pneumatic actuator 14 (pneumatic actuator) operable to apply a pressing force to a pressure plate 16 to engage a clutch disc 18 between the pressure plate 16 and the flywheel 10.
The clutch disc 18 is splined to an input shaft 20 of a transmission (not shown) arranged at the output side of the air clutch. A cylindrical shaft 24 is fitted around the shaft 20 through a bushing 22. The clutch cover 12 is fitted around the right end of the cylindrical shaft 24 in FIG. 4.
The left end of the shaft 24 is surrounded by a cover 26, in which a chamber 28 is formed. Two air seals 30a, 30b are interposed between the cover 26 and the shaft 24 to prevent leakage of the air, as will be detailed later.
The cover 26 is connected to a control valve 32 or inching valve, which is adapted to be operated by a clutch pedal 31 and to flow the air supplied from a compressor 34 through a regulator valve 36, a chamber 38 between the air seals 30a, 30b, and an inlet port 40 of the shaft 24 into a passage 42. The left end of the passage 42 is connected through an outlet port 44 and a passage 46 formed in a wall of the clutch cover 12 to an air chamber 48 in the pneumatic actuator 14.
In this known structures, the control valve 32 is connected to the clutch pedal 31 through a rod, and the clutch can not be operated by a hydraulic pressure from a master cylinder.
Further, a pressure control valve may be used as the control valve 32, in which case it is impossible to obtain such a usual pedal operation feeling that the force for operating the clutch pedal 31 gradually increases as the operation (stepped-on) quantity of the pedal 31 increases, resulting in difficulty in the clutch operation or manipulation.
Objects of the Invention
A first object of the invention is to provide an air pressure control valve of an air clutch in which an air pressure supplied to the air clutch can be controlled by a hydraulic pressure from a master cylinder, the clutch can be easily operated, and its axial length is so short that it can be easily mounted on an automobile.
Other and further objects and advantages of the invention will appear more fully from the following description of the embodiments.
Summary of the Invention
(1) Technical Means
The present invention provides an air pressure control valve of an air clutch wherein an air valve assembly interlocking with an operated quantity of a clutch pedal for controlling an air pressure supplied from an air pressure source to the air clutch, and a first valve body for supplying the air pressure from the air pressure source to the air clutch when the clutch is engaged and a second valve body interlocking with the clutch pedal for releasing the air pressure to be supplied to the air clutch when the clutch is disengaged are provided in the air valve assembly; characterized in that a first spring member is provided in a cylindrical body fixed to the air valve assembly, the spring force of the first spring member and a pneumatic force against a diaphragm connected to the second valve body are operable to set a maximum air pressure, a rod related to the second valve body is slidably disposed in the cylindrical body, the rod is connected to a piston for receiving a hydraulic force from a master cylinder which transform the operated quantity of the clutch pedal into the hydraulic force, second and third spring members operating in series are concentrically disposed between the rod and the second valve body, a spring force transmitting mechanism is arranged for transmitting the spring force of the second and third spring members to the second valve body, and air pressure characteristics suitable for clutch controlling is obtained by a position of the piston slided by the hydraulic pressure from the master cylinder interlocking with the clutch pedal.
(2) Operation
In the stepped-on operation of the clutch pedal, as the hydraulic pressure against the piston increases, the force against the second valve body by the spring force transmission mechanism decreases, so that such air pressure characteristics are obtained that the air pressure to the air clutch gradually decreases.
Since the spring force transmission mechanism has a short axial length due to the concentrically arranged second and third spring members, the whole length of the air control valve is short, which facilitates mounting thereof to automobiles.